JPS6345557B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for treating the structure of a fast neutron nuclear reactor.

The core of a fast neutron reactor usually consists of an elongated box containing a group of coated needles or rods containing fissile or fuel parent material. At the upper end of the box there are gripping heads which allow each assembly to be raised and transported. In their lower part, the boxes have a base that allows them to be positioned in the reactor core between adjacent structures by engaging them in a horizontal support grid.

In fast neutron reactors, the reactor core is generally constructed by grouping such structures into vertically axed vessels containing an appropriate amount of liquid-cooled metal, usually sodium. This vessel is a protective enclosure that is open at the top and has thick concrete walls and is closed by a horizontal slab above the free level of the liquid metal and insulated from the liquid metal by a layer consisting of a covering neutral gas. hung above. In particular for introducing or removing structures in relation to the reactor core, access to the reactor core through the slab is provided by a device having two rotating plugs, the two rotating plugs being relatively eccentric. and attached to the opening in the slab in such a way that their combined rotation brings the gripper into a vertical position relative to any structure, said gripper being supported by one of said plugs and above the slab. installed at the lower end of the poker, which is controlled from outside the container. Such equipment was introduced in 1973
The application was filed on June 27, 2015 in the name of Commissaria a Renergi Atomic (Atomic Energy Commission) and entitled "Method for treating irradiated fuel structures in fast neutron nuclear reactors and apparatus for carrying out this method." Described in a French patent.

However, devices similar to those described above have large container diameters. The cost of such containers, and especially the stainless steel required to manufacture them, is therefore high.

The present invention relates to an apparatus and method for processing the structure of a fast neutron reactor, making it possible to obtain large rotating plugs with a smaller diameter than currently known solutions. It is therefore possible to reduce the vessel diameter, which makes the raw materials significantly more economical, and to reduce the cost of the reactor.

In particular, the present invention relates to a reactor core constituted by a group of structures arranged in a vertically arranged vessel and positioned in a support grid, a horizontal slab above said vessel, and a a small rotating plug within and eccentric with respect to the large rotating plug; and a treatment pot or container allowing the fuel element to be removed from said container, said small rotating plug being connected to a treatment pot. a large rotating plug having a handle and positioned coaxially in relation to the reactor core, the handler having a processing arm that allows the poker to reach and support a portion of the structure, particularly a structure in the center of the core; transportable to a pick-up station of the grid, and structures placed on the pick-up station as well as structures in a peripheral area accessible downwardly to the processing arm are placed by the processing arm into the processing pot or container; The present invention relates to a device for processing the structure of a fast neutron nuclear reactor.

The fast neutron reactor structure ejector according to the invention forms a pick-up station by removing one or more structures, if not already present, and lifts the structures from the central area of the reactor core by means of a poker. The reactor core is transported to a station, these structures are picked up by a processing arm and transported from the station into a processing pot, and the surrounding structures of the reactor core are transported directly into the processing pot by the processing arm.

The invention will be explained in more detail below with reference to non-limiting examples and the accompanying drawings, in which: FIG.

FIG. 1 is a sectional view of a fast neutron reactor including a handling installation according to the invention. The reactor includes a vertically arranged main vessel 2 suspended from a horizontal slab 4 and filled with liquid cooled metal, typically sodium. The level of liquid sodium is overcome by a layer of inert gas, usually consisting of argon. The horizontal slab 4 rests on a thick-walled concrete enclosure 6. The core 8 of the nuclear reactor within the replenishment or inner vessel 9 which defines two separate zones within the main vessel is essentially submerged by a parent fuel structure immersed in liquid sodium and located in a support grid 13. It is composed of In its upper part, each assembly has a processing head which allows the assembly to be extracted from the core 8 and then transported into a processing vessel or pot 10 positioned around the periphery of the core. The pot 10 is movable along a ramp 11 that occurs within the container 2 and crosses the upper slab 4. This type of pot was published on May 28, 1971 by the Commissaria a Renergi.
It is described in French Patent No. 7119431 filed in the name of Atomic (Atomic Energy Commission) and entitled ``Treatment pot for fuel structures''.

The horizontal slab 4 has a circular opening in which there are two rotating plugs, namely a large rotating plug 12 with a relatively eccentric center O;
A structure consisting of a small rotating plug 14 of O' is attached. According to the invention, the small plug 14 has a treatment poker 16. A gripping tongue 18 capable of gripping the structure of the reactor core 8 is provided at the lower end of the poker.

Processing arm 20 installed on large rotating plug 12
is a vertical body across a large rotating plug and a core 8
It is constituted by a horizontal beam terminated by gripping scissors 24 capable of gripping a structure consisting of. A handling arm of this type is described and claimed, for example, in French Patent No. 142,624, filed on March 6, 1968 in the name of Commissaria a Renergi Atomic and entitled "Handling Arm". There is.

After being placed in the pot 10, the structure is placed on the ramp 1
1 and removed from the container 2 to the outside of the slab 4. The pot 10 is then placed in a pivot member 26 which is connected to a second ramp 28.

FIG. 2 is a cross-sectional view of the nuclear reactor of FIG. 1 showing the transport of the structure from the peripheral area of the core to pot 10. FIG. 2 also shows a main container 2 with an inner container 9;
The processing arm 20 with its horizontal beam 22, pot 10, ramp 11 and core 8 are shown.

If l is the distance separating the vertical axis of rotation of the processing arm 20 from the vertical axis of the processing scissors 24, then the center of the area that can be reached by the scissors 24 that terminates in the processing arm into the reactor core structure is large. It is clear that there is a ring in the center of the rotating plug and whose width is equal to 2l, ie twice the length of the horizontal beam of the processing arm. On the core this ring defines an area 30 called the peripheral area,
Within that area the structure can be directly accessed by the processing arm. Structures irradiated within this area can be removed in one operation of the processing arm. Appropriate rotation of the large rotary plug 12, followed by rotation of the processing arm, makes it possible to bring the gripping shears 24 over the structure to be removed. The fuel structure is then transferred into the pot 10 and then placed in the reactor vessel 2 in a manner known per se.
can be removed from

The remainder of the core 8, that area which does not form part of the peripheral area 30, is called the central area 32.
The structure located within this central area is the processing arm 2.
0 cannot be reached directly. The removal of the illumination structure arranged in the central area 32 is carried out according to the invention in the following manner. That is, in the peripheral area 30, a place is provided as a picking station P to which the fuel structure located in the central area is first transferred, and then the fuel structure is picked up from there and transported to the pot 10, or it is specially provided. If not, the processing arm 20
by removing one or more fuel structures from the surrounding area.
is formed. The fuel assembly located in the central area of the core is then transferred to this lifting station P by means of a poker placed on a small rotating plug or by means of a poker mounted during reactor shutdown instead of a control bar mechanism.

Removal and evacuation of the fuel structure by the apparatus of the present invention is illustrated in FIG. Structure a is located in the central area 32 of the core. Appropriate rotation of the small plug 14 causes the poker 16 (see Fig. 1) to be placed above the structure a.
I'll bring it. Rotation of small plug 14 in the direction of arrow 34 brings assembly a to position a'. Rotation of the large plug according to arrow 36 brings it above the picking station P generated in the peripheral area 30. A large plug is then set downwards. By appropriately rotating the plug 12, the gripping scissors 24 of the arm 20 can be picked up and brought above the station P. As mentioned above, the structure a positioned at the station P is
It is picked up by arm 20 and then transported into pot 10. Structure a is then removed from the reactor vessel in a manner known per se.

A portion of the fuel structure can be removed directly from the reactor core by the processing arm 20.
There is therefore no need for it to pass through a pick-up station. However, in order to be able to remove the device consisting of the irradiation structure, it is necessary to provide a poker for a portion of the fuel structure of the core 8 on the small rotating plug 14.

In order to more clearly illustrate the large rotating plug diameter reductions allowed by the present invention, two explicitly numerical examples are presented below for a special reference core.

Embodiment According to a first embodiment, the horizontal beam 2 of the processing arm
The length of 2 is 1476mm, and the radius of the small rotating plug is
3276mm, and the eccentric radius between the two plugs is 900
mm. In this case, effectively off-axis with the core, the large rotating plug must have a radius of 4726 mm.

The radius of this large rotating plug of 4726 mm can be compared with the radius of the reactor with the same reference core, in which the structure was mounted on a small rotating plug with a radius of 3561 mm and an eccentric radius of 1185 mm with respect to the large rotating plug. Only one or two pokers are processed. The radius of the large rotating plug in this case must be 5296 mm, although its axis is eccentric with respect to the core axis. This radius was therefore reduced by 500mm.

With this solution, 92% of the core structure can be reached by the poker, and the remaining 8% can be approached directly by the arm.

Example According to the second example, the length of the beam 22 is 2706
mm, the radius of the small rotating plug is increased to 3561 mm, and the radius of the large rotating plug is increased to 4726 mm, and the eccentric radius of these plugs is 1185 mm, which is the same as the eccentric radius of the example. In this case only 9% of the structures require advance transport of the boker to the pick-up station, the remaining 91% can be approached directly by the arm. Therefore, a reduction in the diameter of a large rotating plug is obtained at the cost of only a small amount of complexity in the operation of the fuel assembly.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a fast neutron reactor including a device for processing the structure according to the invention; FIG. 2 shows the structure with a processing arm shown on a large rotating plug from the peripheral area of the core to the processing pot; Figure 3 is a sectional view of the nuclear reactor of Figure 1 showing the transport of the structure from the central area of the core to its peripheral area by means of pokers attached to small rotating plugs. FIG. In the figure, 2 is the main vessel, 4 is the slab, 8 is the core,
9 is an inner container, 10 is a processing pot, 12 is a large rotating plug, 14 is a small rotating plug, 16 is a poker, 20 is a processing arm, and P is a picking station.

Claims (1)

[Scope of Claims] 1. A treatment device for structures of a fast neutron reactor, comprising: a core consisting of a group of structures arranged in a vertically arranged vessel and positioned in a support grid; and a horizontal structure above the vessel. a slab; a large rotating plug within said slab; a small rotating plug within said large rotating plug and eccentric to said large rotating plug; and a treatment pot allowing fuel elements to be removed from said vessel; a small rotating plug with a treatment poker, and a large rotating plug located coaxially with respect to the core with a treatment arm, said poker being particularly suitable for the structure in the central part of the core. parts of the structure in the central part of the core, which are outside the range of reach of said processing arm, and which are removed from the central part of the core. The structures transported to the station P, or structures at the periphery of the part of the structure in the center of the core, can be picked up by the processing arm and thereby placed in a processing pot or vessel. A processing device for the structure of a fast neutron nuclear reactor, which is characterized by the following: